Categories and specific style / wp-title

Hello! I start this thread to make two questions regarding WordPress 4.3. I’m trying to make a function to assign a specific post-style for each category and also display the first post in a different way. So, on the index.php page I put this code:

<?php if ( have_posts() ) : ?>
            <?php $post = $posts[0]; $c=0;?>
            <?php query_posts($query_string . '&cat=1,2'); ?>
			<?php /* Start the Loop */ ?>
			<?php while ( have_posts() ) : the_post() ?>
            <?php $c++;
			if( $c == 1) :?>
<div id="content-news-article-sticky">
<div id="<?php
if ( in_category('A') || is_category('A')) {
	echo 'content-article-A';
} elseif ( in_category('B') || is_category('B')) {
	echo 'content-article-B';
} elseif ( in_category('C') || is_category('C')) {
	echo 'content-article-C';
} else {
	echo 'content-article-A';
}
?>"><a href="<?php the_permalink(); ?>" rel="bookmark" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a></h2>
<p><?php the_excerpt(); ?></p>

            <?php else :?>
				<?php get_template_part( 'content', get_post_format() ); ?>
            <?php endif;?>
			<?php endwhile; ?>

Assuming A, B, and C are the category slugs, but it didn’t work. The posts get content-article-A style.

Also I’m having some problems with the title of the page. Instead the SITE NAME | DESCRIPTION, the browser shows the site url on the title of the page. I was using wp_title function and now tried with add_theme_support( ‘title-tag’ ); on function.php but it didn’t work.

Thanks in advance! =)